1. Field of the Invention
The invention concerns a process for texturing an HTc superconductor of the matrix type based on silver and the superconductor material (Bi.sub.1-x Pb.sub.x).sub.2 Sr.sub.2 Ca.sub.y Cu.sub.1+y O.sub.6+2y where x.epsilon.[0; 0,4] and y.epsilon.{0, 1, 2}, and a superconductor of this kind textured by this process. The invention is more particularly concerned with a silver-based matrix multifilament superconductor.
2. Description of the Prior Art
HTc superconductors of the matrix type based on silver and the superconductor material (BI.sub.1-x PBS.sub.x).sub.2 SR.sub.2 Ca.sub.y Cu.sub.1+y O.sub.6+2y where x.epsilon.[0; 0,4] and y.epsilon.{0, 1, 2} towards the superconductor phase is effected by heat treatment. Texturing processes typically comprise the following steps:
raising the temperature of the superconductor from room temperature to the melting point of the superconductor material; PA1 maintaining the temperature of the superconductor constant for a relatively short time at the melting point of the superconductor material; PA1 reducing the temperature of the superconductor from the melting point of the superconductor material to the temperature of synthesis of the superconductor material at a temperature gradient in the order of 1.degree. C. to 5.degree. C. per hour; PA1 maintaining the temperature of the superconductor constant for a relatively long time (between 25 hours and 70 hours) at the temperature of synthesis of the superconductor material; and PA1 reducing the temperature of the superconductor from the temperature of synthesis of the superconductor material to room temperature. PA1 raising the temperature of the superconductor from room temperature to the melting point of the superconductor material, PA1 maintaining the temperature of the superconductor constant at the melting point of the superconductor material for a relatively short time, PA1 varying the temperature of the superconductor between the melting point of the superconductor material and its synthesis temperature PA1 maintaining temperature of the superconductor constant at the synthesis temperature of the superconductor material for a relatively long time, and PA1 reducing the temperature of the superconductor from the synthesis temperature of the superconductor material to room temperature, PA1 in which process the step of varying the temperature of the superconductor between the melting point of the superconductor material and its synthesis temperature comprises:
In the case of multifilament superconductors texturing produces a very high current transmission capacity.
However, reducing the temperature of the superconductor between the melting point of the superconductor material and its synthesis temperature at the rate of 1.degree. C. to 5.degree. C. per hour takes several hours. During this period the components constituting the superconductor material, which are molten and highly reactive, form dendritic inserts through the silver matrix. Because of this, the decoupling of the filaments 3 is very poor (FIG. 1). The presence of many short-circuits 1 restricts the use of such superconductors to direct current applications.
Using HTc multifilament superconductors for alternating currents causes induced current losses. It is known to reduce such losses by twisting the superconductor with a small lay and reducing the diameter of the filaments. However, this is effective only if the filament are electrically decoupled from each other by a resistive barrier.
An aim of the present invention is to propose a method of texturing HTc superconductors of the matrix type based on silver and the superconductor material (Bi.sub.1-x Pb.sub.x).sub.2 Sr.sub.2 Ca.sub.y Cu.sub.1+y O.sub.6+2y where x.epsilon.[0; 0,4] and y.epsilon.{0, 1, 2} towards the superconductor phase which limits the formation of such inserts.
Another aim of the present invention is to propose a multifilament HTc superconductor of the matrix type based on silver and the superconductor material (Bi.sub.1-x Pb.sub.x).sub.2 Sr.sub.2 Ca.sub.y Cu.sub.1+y O.sub.6+2y where x.epsilon.[0; 0, 4] and y.epsilon.{0, 1, 2} having performance in terms of current density better than 2 400 A/mm.sup.2 and sufficient inter-filament decoupling for alternating current applications.